openstreetmap-website/app/assets/openlayers/SimpleLayerSwitcher.js

var SimpleLayerSwitcher = OpenLayers.Class(OpenLayers.Control, {
    layerStates: null,
    layersDiv: null,
    ascending: true,

    initialize: function(options) {
        OpenLayers.Control.prototype.initialize.apply(this, arguments);
        this.layerStates = [];
    },

    destroy: function() {
        OpenLayers.Event.stopObservingElement(this.div);

        //clear out layers info and unregister their events 
        this.map.events.un({
            "addlayer": this.redraw,
            "changelayer": this.redraw,
            "removelayer": this.redraw,
            "changebaselayer": this.redraw,
            scope: this
        });
        OpenLayers.Control.prototype.destroy.apply(this, arguments);
    },

    setMap: function(map) {
        OpenLayers.Control.prototype.setMap.apply(this, arguments);

        this.map.events.on({
            "addlayer": this.redraw,
            "changelayer": this.redraw,
            "removelayer": this.redraw,
            "changebaselayer": this.redraw,
            scope: this
        });
    },

    draw: function() {
        OpenLayers.Control.prototype.draw.apply(this);
        this.loadContents();
        this.redraw();
        return this.div;
    },

    checkRedraw: function() {
        var redraw = false;
        if ( !this.layerStates.length ||
             (this.map.layers.length != this.layerStates.length) ) {
            redraw = true;
        } else {
            for (var i=0, len=this.layerStates.length; i<len; i++) {
                var layerState = this.layerStates[i];
                var layer = this.map.layers[i];
                if ( (layerState.name != layer.name) ||
                     (layerState.inRange != layer.inRange) ||
                     (layerState.id != layer.id) ||
                     (layerState.visibility != layer.visibility) ) {
                    redraw = true;
                    break;
                }
            }
        }
        return redraw;
    },

    redraw: function() {
        if (!this.checkRedraw()) {
            return this.div;
        }

        this.div.innerHTML = '';
        var len = this.map.layers.length;
        this.layerStates = [];
        for (var i = 0; i < this.map.layers.length; i++) {
            var layer = this.map.layers[i];
            this.layerStates[i] = {
                'name': layer.name,
                'visibility': layer.visibility,
                'inRange': layer.inRange,
                'id': layer.id
            };
        }

        var layers = this.map.layers.slice();
        if (!this.ascending) { layers.reverse(); }
        for (var i = 0; i < layers.length; i++) {
            var layer = layers[i];
            var baseLayer = layer.isBaseLayer;

            if (layer.displayInLayerSwitcher && baseLayer) {
                var on = (baseLayer) ? (layer == this.map.baseLayer)
                          : layer.getVisibility();
                var layerElem = document.createElement('a');
                layerElem.id = this.id + '_input_' + layer.name;
                layerElem.innerHTML = layer.name;
                layerElem.href = '#';

                OpenLayers.Element.addClass(layerElem, 'basey');
                OpenLayers.Element.addClass(layerElem,
                    'basey-' + (on ? 'on' : 'off'));

                if (!baseLayer && !layer.inRange) {
                    layerElem.disabled = true;
                }
                var context = {
                    'layer': layer
                };
                OpenLayers.Event.observe(layerElem, 'mouseup',
                    OpenLayers.Function.bindAsEventListener(
                        this.onInputClick,
                        context)
                );

                this.div.appendChild(layerElem);
            }
        }

        return this.div;
    },

    onInputClick: function(e) {
        if (this.layer.isBaseLayer) {
            this.layer.map.setBaseLayer(this.layer);
        } else {
            this.layer.setVisibility(!this.layer.getVisibility());
        }
        OpenLayers.Event.stop(e);
    },

    updateMap: function() {

        // set the newly selected base layer
        for(var i=0, len=this.baseLayers.length; i<len; i++) {
            var layerEntry = this.baseLayers[i];
            if (layerEntry.inputElem.checked) {
                this.map.setBaseLayer(layerEntry.layer, false);
            }
        }

        // set the correct visibilities for the overlays
        for(var i=0, len=this.dataLayers.length; i<len; i++) {
            var layerEntry = this.dataLayers[i];
            layerEntry.layer.setVisibility(layerEntry.inputElem.checked);
        }

    },

    loadContents: function() {
        //configure main div
        OpenLayers.Event.observe(this.div, 'mouseup',
            OpenLayers.Function.bindAsEventListener(this.mouseUp, this));
        OpenLayers.Event.observe(this.div, 'click',
                      this.ignoreEvent);
        OpenLayers.Event.observe(this.div, 'mousedown',
            OpenLayers.Function.bindAsEventListener(this.mouseDown, this));
        OpenLayers.Event.observe(this.div, 'dblclick', this.ignoreEvent);
    },

    ignoreEvent: function(evt) {
        OpenLayers.Event.stop(evt);
    },

    mouseDown: function(evt) {
        this.isMouseDown = true;
        this.ignoreEvent(evt);
    },

    mouseUp: function(evt) {
        if (this.isMouseDown) {
            this.isMouseDown = false;
            this.ignoreEvent(evt);
        }
    },

    CLASS_NAME: "SimpleLayerSwitcher"
});